JP6235377B2 - FUEL CELL SYSTEM, CONTROL DEVICE FOR FUEL CELL SYSTEM, AND METHOD FOR CONTROLLING FUEL CELL SYSTEM - Google Patents

Description

  The present invention relates to a fuel cell system including a fuel cell such as a solid oxide fuel cell, a control device for the fuel cell system, and a control method for the fuel cell system.

  Conventionally, as a fuel cell system including a fuel cell that generates electricity using an oxidant gas (for example, oxygen in the air) and a fuel gas (for example, hydrogen), for example, solid oxidation using a solid electrolyte (solid oxide) There is known a fuel cell system including a physical fuel cell.

  As the fuel cell, for example, a fuel cell stack in which a plurality of fuel cell cells each having a plate-like single cell provided with a fuel electrode and an air electrode on both sides of a solid electrolyte layer is used.

  In addition, as the above-described fuel cell system, a desulfurizer that deflows a raw fuel gas such as city gas, or the like that vaporizes water to generate water vapor is provided upstream of a flow path for supplying fuel gas to the fuel cell. Generator, reformer that reacts raw fuel gas and water vapor to reform to hydrogen-rich fuel gas, transformer that modifies carbon monoxide contained in fuel gas to carbon dioxide, further reduce carbon monoxide The thing provided with the hydrogen containing gas production | generation apparatus which consists of a carbon monoxide selective oxidizer for this is disclosed (refer patent document 1).

  Further, in this type of fuel cell system, as shown in FIG. 6 (a), the reformed water tank P1 for storing the reformed water from the upstream side of the reformed water flow path, and the reformed water downstream ( A system including a reforming water pump P2 supplied to the filter P3 side, a filter P3 for purifying the reforming water (which is a pressure loss body), a flow rate sensor P4 for measuring the flow rate of the reforming water, and a power generation module P5 is known. ing. The power generation module P5 includes a vaporizer P6, a reformer P7, a fuel cell stack P8, and the like.

JP 2009-78969 A

  However, in the fuel cell system as shown in FIG. 6 (a), the filter P3 is a water filter that is constantly immersed in the reformed water. Therefore, when the operation of the fuel cell system is stopped, FIG. As shown in b), due to the residual pressure downstream of the filter P3, the reformed water remaining downstream of the filter P3 may flow into the fuel cell stack P8 (specifically, inside the fuel cell).

  In particular, when the fuel cell is a solid oxide fuel cell (SOFC) that becomes high temperature during power generation, the reformed water (residual water) remaining downstream of the filter P3 becomes steam and reaches the fuel cell. Then, the fuel electrode of the fuel cell is oxidized, and in the worst case, there is a possibility that damage such as cell cracking of the fuel cell occurs.

  In addition, as the stop of the operation of the fuel cell system, there are an emergency stop at the time of occurrence of a gas leak or the like, and a normal operation stop by operation of a stop button, and there is a high possibility that the above-described problem occurs at the time of an emergency stop. However, in either case, similar problems may occur.

  The present invention has been made in order to solve the above-described problems. The purpose of the present invention is to break down the fuel cell by the reforming water entering the fuel cell when the operation of the fuel cell system is stopped. It is an object of the present invention to provide a fuel cell system, a control device for the fuel cell system, and a control method for the fuel cell system.

(1) The present invention uses, as a first aspect (fuel cell system), a vaporizer that vaporizes reformed water used for reforming raw fuel into fuel gas, and the fuel gas and oxidant gas. In a fuel cell system comprising a power generation module having a fuel cell stack in which fuel cells for generating power are stacked, a flow path for supplying the reformed water to the vaporizer is provided upstream from the reformed water. A tank for storing the reforming water, a pump for pumping the reforming water from the tank and supplying the reforming water to the carburetor side on the downstream side, and being held in a state immersed in the reforming water, A filter for purifying the reforming water, a supply valve disposed between the filter and the vaporizer and opening and closing the flow path, and disposed between the supply valve and the vaporizer. Flow rate for measuring the flow rate of the reforming water And capacitors, provided with a, the filter and the branch flow path branched and connected to the tank from the flow path between the supply valve is disposed in the branch passage, opening and closing the branch passage And a discharge valve.

  In the first aspect, since the supply valve is provided between the filter and the vaporizer, in order to stop the operation of the fuel cell system, when the supply operation of the pump that supplies the reforming water is stopped, By closing the flow path of the reforming water by the supply valve, it is possible to prevent the reforming water remaining between the filter and the vaporizer from entering the vaporizer and being vaporized. Can be prevented from flowing into the fuel cell stack (specifically, the fuel cell).

  In the first aspect, when the operation of the fuel cell system is stopped, the pressure of the reformed water (residual pressure) remaining between the filter and the vaporizer is opened by opening the discharge valve of the branch flow path. Therefore, at the time of restart (when the operation for power generation is resumed), the supply valve can be opened with the residual pressure lowered. Accordingly, it is possible to prevent the reformed water from flowing into the vaporizer due to an excessive residual pressure at the time of restart, and the unnecessary generated water vapor from flowing into the fuel cell.

  As described above, in the first aspect, when the pump is stopped, the reformed water (vaporized) can be prevented from flowing into the fuel battery cell. Specifically, the reformed water reaches the fuel electrode. Thus, the fuel electrode can be prevented from being oxidized, and damage such as cell cracking of the fuel cell can be prevented.

  In particular, when the fuel cell is an SOFC, the fuel cell is operated at a high temperature, so that the fuel electrode is oxidized and the fuel cell is easily damaged. However, in this first aspect, the oxidation and damage are effective. Can be prevented.

Moreover, in this 1st aspect, since a reforming water can be returned to a tank from the flow path between a filter and a supply valve by a branch flow path, the reduction | decrease in the amount of reforming water can be suppressed.
Further, in the first aspect, since the reforming water is discharged on the downstream side of the filter, at the time of restart, the purified reforming water that has passed through the filter is supplied to the vaporizer side (and hence the reformer side). Can be supplied to.

(2) As a second aspect of the present invention, the filter is an ion exchange resin filter.
The second aspect exemplifies the types of filters. Since this ion exchange resin filter is a filter in which the ion exchange resin is constantly immersed in the reforming water, when the operation of the fuel cell system is stopped, the filter, the supply valve, It is possible to prevent the reformed water remaining during the period from flowing back to the filter and degrading the filter performance.

  (3) In the third aspect of the present invention, as the third aspect, the supply valve and the discharge valve are configured such that the flow path of the reformed water is changed to the flow path and the branch flow path between the filter and the supply valve. It is characterized by being integrally formed as a switchable three-way valve.

  The third aspect exemplifies that the supply valve and the discharge valve are configured as a three-way valve. Therefore, by the operation of the three-way valve, for example, during operation, the flow path (main flow path) between the filter and the vaporizer is opened, and the flow path (branch flow path) between the main flow path and the tank is closed. When stopping, the main flow path can be closed and the branch flow path can be opened.

This has the advantage that control of the opening and closing operation of the valve becomes easy.
(4) The present invention is characterized in that as a fourth aspect, a temperature sensor for measuring the temperature of the fuel cell stack is provided.

  For example, when the stop of the operation of the fuel cell system is instructed to stop the operation, if the stop of the operation is instructed when the fuel cell stack is in a high temperature state, a malfunction occurs. There is. For example, when the fuel cell stack is operated at a high temperature (for example, 700 ° C.), for example, if the supply of fuel gas is stopped immediately, the fuel electrode is likely to be oxidized.

  Therefore, the temperature of the fuel cell stack is measured by the temperature sensor, and when the temperature is sufficiently lowered (for example, 400 ° C.) that the fuel electrode is difficult to oxidize, the operation of the fuel cell system is stopped such as supply of fuel gas. Thus, oxidation of the fuel electrode and damage to the fuel battery cell can be suppressed.

(5) As a fifth aspect of the present invention, a reformer for reforming the raw fuel into the fuel gas is provided on the downstream side of the vaporizer.
In the fifth aspect, as described above, when the supply operation of the pump that supplies the reforming water to stop the operation of the fuel cell system is stopped, the flow path of the reforming water is closed by the supply valve. Can prevent the reformed water remaining between the filter and the vaporizer from entering the vaporizer and steaming, thereby preventing the steam from flowing into the reformer and into the fuel cell stack. it can. That is, the catalyst (for example, nickel catalyst) filled in the reformer and the fuel electrode of the fuel cell stack may be destroyed by the inflow of water vapor in the above-described situation. Damage can be prevented.

  (6) The present invention provides a fuel cell system control apparatus for controlling a fuel cell system according to any one of the first to fifth aspects, as a sixth aspect (control apparatus for a fuel cell system), wherein the fuel cell system A supply valve control means for controlling the opening and closing of the supply valve, a discharge valve control means for controlling the opening and closing of the discharge valve, and a pump control for controlling the operation of the pump when a condition for stopping the operation of the pump is satisfied Means.

  In the sixth aspect, when the condition for stopping the operation of the fuel cell system is satisfied, the supply valve is closed by the supply valve control means, so that the reformed water flows into the vaporizer and is vaporized. It is possible to prevent water vapor from flowing into the fuel cell stack and oxidizing the fuel electrode or damaging the fuel cell. Further, by opening the discharge valve by the discharge valve control means, the residual pressure of the reformed water remaining between the filter and the vaporizer can be released and the reformed water can be returned to the tank. Furthermore, the supply of the reforming water can be stopped by stopping the operation of the pump by the pump control means.

  Here, as the stop of the operation of the fuel cell system, not only the operation of generating power by the fuel cell system is actually stopped, but also the stop of the operation state other than the power generation (for example, the start operation state, the standby state) is instructed. An operation is also mentioned. The operation of stopping the operation of the fuel cell system includes an operation of stopping power generation, such as stopping the operation of supplying fuel gas or oxidant gas to the fuel cell stack.

  (7) The present invention provides a fuel cell system control method for controlling a fuel cell system according to any one of the first to fifth aspects, as a seventh aspect (control method of the fuel cell system), wherein the fuel cell system When the condition for stopping the operation of is satisfied, control for closing the flow path between the filter and the supply valve by the supply valve, control for opening the branch flow path by the discharge valve, And control to stop the pump.

  In the seventh aspect, when the condition for stopping the operation of the fuel cell system is satisfied, the supply valve controls the flow path (main flow path) between the filter and the supply valve to perform reforming. It is possible to prevent water vapor from flowing into the vaporizer and vaporized from flowing into the fuel cell stack to oxidize the fuel electrode and damage the fuel cell. Further, by performing control to open the branch flow path using the discharge valve, it is possible to release the residual pressure of the reformed water remaining between the filter and the vaporizer and return the reformed water to the tank. . Furthermore, the supply of further reforming water can be stopped by performing control to stop the pump.

  (8) The present invention, as an eighth aspect, is characterized in that the condition for stopping the operation of the fuel cell system includes a condition in which the temperature of the fuel cell stack has become a predetermined temperature or less.

The eighth aspect illustrates conditions for stopping the operation of the fuel cell system.
When the temperature of the fuel cell stack falls below a predetermined temperature, the fuel electrode is difficult to oxidize and damage to the fuel cell is unlikely to occur, so the operation of the fuel cell system is stopped (for example, fuel gas Even if the supply of the fuel cell is stopped, oxidation of the fuel electrode and damage to the fuel cell are unlikely to occur.

  That is, when the temperature of the fuel cell stack becomes equal to or lower than a predetermined temperature, the operation can be suitably stopped while suppressing the oxidation of the fuel electrode and the damage of the fuel cell by stopping the operation. .

  The temperature of the fuel cell stack is a temperature (for example, a stop temperature of 400 ° C.) at which the fuel electrode is hardly oxidized and the fuel cell is not easily damaged even when the operation of the fuel cell system is stopped. Can be sought.

  Here, the temperature of the fuel cell stack includes the temperature of the side surface of the fuel cell stack (the side surface in the direction perpendicular to the stacking direction (end portion direction)). The reason for measuring the temperature of this side surface is that it is considered that the temperature inside the fuel cell stack is more accurately shown than the temperature at the end in the stacking direction.

  In addition, since the temperature of the side surface of the fuel cell stack and the temperature of other parts (for example, the temperature of the end portion) have a predetermined relationship, the temperature of the fuel cell stack other than the side surface is adopted. You can also

Hereinafter, each configuration of the present invention will be described.
Examples of the fuel cell stack include a solid oxide fuel cell (SOFC) using a ZrO ₂ -based ceramic as an electrolyte, a solid polymer fuel cell (PEFC) using a polymer electrolyte membrane as an electrolyte, Li-Na / Examples of the fuel cell stack include a molten carbonate fuel cell (MCFC) using a K-based carbonate as an electrolyte and a phosphoric acid fuel cell (PAFC) using phosphoric acid as an electrolyte.

  Note that the operating temperature of the fuel cell stack (that is, the temperature at which ions can move in the electrolyte) differs for each type of fuel cell stack. Specifically, the operating temperature of SOFC is about 700 ° C. to 1000 ° C., the operating temperature of PEFC is about room temperature to about 90 ° C., the operating temperature of MCFC is about 650 ° C. to 700 ° C., and the operating temperature of PAFC is 150 ° C. to 200 ° C. It is about ℃.

As the fuel cell, for example, a configuration including a single cell in which a fuel electrode layer, a solid electrolyte layer, and an air electrode layer are integrally laminated can be adopted.
As the raw fuel, various raw material gases capable of generating hydrogen by reforming, such as natural gas (for example, LNG), city gas, LPG, kerosene, methanol, biomethanol, and the like can be employed.

Here, the fuel gas indicates a gas containing a reducing agent (for example, hydrogen) serving as a fuel, and the oxidant gas indicates a gas (for example, air) containing an oxidant (for example, oxygen).
A reformer refers to reforming raw fuel gas to a composition suitable for power generation when fuel gas is supplied to a fuel cell (for example, reforming city gas or the like to a gas having a higher hydrogen component). ).

It is explanatory drawing which shows the whole structure of the fuel cell system of an Example. It is a block diagram which shows the electric constitution of the fuel cell system of an Example. It is a flowchart which shows the process at the time of the stop of the driving | operation by the controller of the fuel cell system of an Example. It is a flowchart which shows the process at the time of starting of the driving | operation by the controller of the fuel cell system of an Example. It is a timing chart which shows the operation | movement in the stop and restart of the driving | operation of the fuel cell system of an Example. FIG. 2 shows a conventional technique, (a) is an explanatory diagram showing a configuration of a fuel cell system, and (b) is a timing chart showing its operation.

  Next, a solid oxide fuel cell system will be described as an example for implementing the fuel cell system, the fuel cell system control device, and the fuel cell system control method of the present invention.

a) First, the overall configuration of the solid oxide fuel cell system will be described. In the following description, the “solid oxide form” is omitted. As shown in FIG. 1, the fuel cell system 1 of this embodiment is a fuel gas (for example, a reformed gas obtained by reforming a city gas of a raw fuel gas). And an oxidant gas (for example, air), and more specifically, a power generation unit that generates power by receiving supply of hydrogen and oxygen.

  In this fuel cell system 1, along the reforming water supply path (main flow path) 3, from the upstream side, the reforming water tank 5, the reforming water pump 7, the filter 9, the supply valve 11, the flow sensor 13, the power generation A module 15 is arranged. In the reforming water supply path 3, the reforming water tank 5 side is the upstream side and the fuel cell stack 23 side is the downstream side.

  The power generation module 15 is disposed in a heat insulation container 17, and in the heat insulation container 17, a vaporizer 19, a reformer 21, a fuel cell stack (power generation stack) 23, and a temperature sensor (stack temperature sensor) 25. Has been placed.

In addition, a branch flow path 27 is provided from the main flow path 3 between the filter 9 and the supply valve 11 to the reformed water tank 5, and a discharge valve 29 is provided in the branch flow path 27. ing.
The fuel cell system 1 further includes a controller 31 that controls the operation of the fuel cell system 1, and a stop button 33 and a start button 35 are connected to the controller 31.

Hereinafter, each configuration will be described in detail.
The reforming water tank 5 is a water tank that stores the reforming water used when reforming the raw fuel gas, and the reforming water pump 7 is a downstream side of the reforming water pumped up from the reforming water tank 5. This is a pump that supplies the filter 9. The operation of the reforming water pump 7 is controlled by the controller 31.

  The filter 9 is an ion exchange resin filter (water filter) that purifies the reformed water, and is always filled with the reformed water so that the ion exchange resin is immersed in the reformed water. In other words, the ion exchange resin is held in a state of being immersed in the modified water.

The supply valve 11 is an electromagnetic valve (water supply valve) that opens and closes the main flow path 3, and its opening and closing is controlled by the controller 31.
The discharge valve 29 is an electromagnetic valve (drainage valve) that opens and closes the branch flow path 27, and its opening / closing is controlled by the controller 31.

The flow sensor 13 is a flow meter that measures the flow rate of the reforming water flowing through the main flow path 3, and the measurement result is output to the controller 31.
The vaporizer 19 is a device that heats the reformed water to vaporize it into steam, and the steam is supplied to the reformer 21.

  The reformer 21 is a device provided with a reforming catalyst (for example, ruthenium or nickel) inside, and the raw fuel gas introduced into the reformer 21 is generated by steam supplied from the vaporizer 19. By steam reforming, a so-called hydrogen-rich fuel gas having a larger proportion of hydrogen than the raw fuel gas is generated.

  Although not shown, the fuel cell stack 23 has a substantially rectangular parallelepiped shape in which a plurality of plate-like fuel cells serving as power generation units are stacked. This fuel cell is a so-called fuel electrode support membrane type fuel cell, a well-known fuel electrode (arranged so as to be in contact with the fuel flow path), a solid electrolyte (for example, made of zirconia), It has a single cell integrated with an air electrode (disposed so as to be in contact with the air flow path).

The temperature sensor 25 is disposed on the side surface (for example, the central portion) of the fuel cell stack 23 and detects the temperature of the side surface.
Although not shown, in addition to the configuration described above, the power generation module 15 has an exhaust gas combustor that burns exhaust gas (including unreacted components) exhausted from the fuel cell stack 23 almost completely, or a fuel cell stack 23. An activation burner for heating the fuel cell stack 23 at the time of activation is disposed.

Further, as shown in FIG. 2, the controller 31 is an electronic control device including a known microcomputer 31a.
The controller 31 is connected to a stop button 33 for instructing to stop the operation of the fuel cell system 1 and an activation button 35 for instructing to start the operation of the fuel cell system 1.

  As described above, the controller 31 receives a signal indicating the flow rate of the reforming water from the flow sensor 13, and receives a signal indicating the temperature of the side surface of the fuel cell stack 23 from the temperature sensor 25.

On the other hand, a control signal for controlling the operation of the reforming water pump 7, the supply valve 11, and the discharge valve 29 is output from the controller 31.
Further, a fuel pump 37 that supplies fuel gas to the fuel cell stack 23, an air pump 39 that supplies air, and an air-fuel mixture pump 41 that supplies a fuel mixture to an activation burner are connected to the controller 31. These operations are controlled by a control signal from.

The controller 31 is a control device for the fuel cell system of the present invention, and functions as a supply valve control means, a discharge valve control means, and a pump control means of the present invention.
b) Next, the operation of the fuel cell system 1 controlled by the controller 31 will be described.

[Processing when operation stops]
First, a process for stopping the fuel cell system 1 during the operation (power generation) of the fuel cell system 1 (a process for stopping power generation) will be described.

As shown in FIG. 3, in step (S) 100, the fuel cell stack 23 generates power as usual.
Specifically, the reforming water pump 7 is operated, the reforming water is supplied to the vaporizer 19 via the (opened) supply valve 11, and steam is generated. The inside of the vessel 21 and the fuel cell stack 23 is purged. In a state where the operation of the reforming water pump 7 is continued, the air pump 39 is operated to supply air to the fuel cell stack 23, and then the fuel pump 37 is operated to convert the raw fuel gas into the reformer 21. To supply. In the reformer 21, the raw fuel gas is reformed using water vapor, and the generated fuel gas is supplied to the fuel cell stack 23. With these start-up operations, the temperature of the fuel cell stack 23 is raised.

  As a result, the fuel cell stack 23 (specifically, the fuel cell) reaches a temperature at which electric power can be generated (for example, 700 ° C.). When the fuel cell stack 23 reaches a temperature at which electric power can be generated, electric power is generated using the supplied fuel gas and air.

  During this power generation, the discharge valve 29 is closed. In addition, an open / close valve (not shown) is usually provided in the supply path of the raw fuel gas, but this open / close valve is naturally opened during power generation.

  In the following step 110, it is determined whether or not a serious abnormality that is a serious abnormality has occurred in the fuel cell system 1. If it is determined that there is a major abnormality, the process proceeds to step 130. On the other hand, if it is determined that there is no major abnormality, the process proceeds to step 120.

For example, when a fuel gas leak is detected (detection of an abnormality by a gas alarm), or when the amount of reforming water is not supplied for a certain period of time, it is determined that a serious abnormality has occurred.
In step 130, the fuel cell system 1 is disconnected from the external load and system (electrical connection is cut off), and the process proceeds to step 160.

  On the other hand, in step 120, it is determined whether there is a normal stop request. If it is determined that there is a normal stop request, the process proceeds to step 140. On the other hand, if it is determined that there is no normal stop request, the process returns to step 100.

For example, when the stop button 33 is operated (turned on), it is determined that there is a stop request.
In step 140, the fuel cell system 1 is disconnected from the external load and system.

  In the subsequent step 150, it is determined whether or not the temperature of the side surface of the fuel cell stack 23 has reached a predetermined stop temperature (a temperature at the time of normal stop: 400 ° C.) or less. Here, if it is determined that it has reached (because the temperature has dropped to a temperature at which operation can be stopped), the routine proceeds to step 160. On the other hand, if it is determined that it has not been reached (because the temperature is still high for stopping operation), the system waits until the temperature decreases.

In step 160, a predetermined process for stopping the operation of the fuel cell system 1 is performed, and this process is temporarily terminated.
Specifically, the supply valve 11 is closed so that the reformed water (residual water) between the filter 9 and the supply valve 11 is not supplied to the power generation module 15 side, and the residual pressure of the residual water is suppressed. . Further, the discharge valve 29 is opened, the reforming water (residual water) between the filter 9 and the supply valve 11 is returned to the reforming water tank 5 side, and the residual water flows back to the filter 9 to function the filter 9. Prevent loss. Furthermore, the pump instruction value of the reforming water pump 7 is set to 0 [cc / min], and the reforming water pump 7 is stopped.

  At the same time, when the operation of the fuel cell system 1 is stopped, “the supply of raw fuel gas (and hence the fuel gas) is stopped by stopping the fuel pump 37”, “the supply of air is stopped by stopping the air pump 39”. In the same manner as the stop of the reforming water pump 7, the process accompanying the stop of power generation is performed after the temperature of the side surface of the fuel cell stack 23 reaches a sufficiently low temperature (for example, 400 ° C.).

[Processing at the start of operation]
Next, processing when starting the fuel cell system 1 while the operation of the fuel cell system 1 is stopped will be described.

  As shown in FIG. 4, in step 200, it is determined whether or not there is a start request for the fuel cell system 1. If it is determined that there is a start request, the process proceeds to step 210. On the other hand, if it is determined that there is no start request, the stopped state is maintained.

For example, when the activation button 35 is operated (turned on), it is determined that there is an activation request.
In step 210, it is determined whether the temperature of the side surface of the fuel cell stack 23 is equal to or higher than a predetermined temperature (vaporizable temperature: for example, 140 ° C.) at which the reforming water charged into the vaporizer 19 is surely vaporized. Here, if it is determined that the temperature is higher than the vaporizable temperature (because it has reached a temperature sufficient for starting the supply of reforming water), the process proceeds to step 220. Wait until the temperature rises (because the temperature is low at the start).

  Here, since the relationship between the temperature of the side surface of the fuel cell stack 23 and the temperature at which the reformed water charged into the vaporizer 19 evaporates is determined in advance by experiments and simulations, the fuel cell stack 23 It is possible to determine the vaporizable temperature from the temperature of the side surface.

When the temperature of the fuel cell stack 23 is low, the fuel cell stack 23 is heated by, for example, an activation burner.
In step 220, a predetermined process for starting the operation of the fuel cell system 1 is performed, the starting operation is continued, and the process proceeds to step 230.

  Specifically, the supply valve 11 is opened so that the reformed water can be supplied from the filter 9 side to the power generation module 15 side. Further, the discharge valve 29 is closed so that the reformed water is not discharged from between the filter 9 and the supply valve 11. Further, the pump instruction value of the reforming water pump 7 is set to a predetermined starting flow rate, and the reforming water pump 7 is operated.

  In step 230, it is determined whether or not the temperature of the fuel cell stack 23 is equal to or higher than a temperature at which power generation is possible. Here, when it is determined that the temperature of the fuel cell stack 23 is equal to or higher than the power generation possible temperature, the start-up operation process is temporarily ended. On the other hand, if it is determined that the temperature is lower than the temperature at which power generation is possible, the startup operation is continued.

  At the same time, when the operation of the fuel cell system 1 is started, “connection of the circuit from the fuel cell stack 23 to the load”, “operation of the fuel pump 37”, “operation of the air pump 39”, etc. Performs processing associated with the start of power generation.

  When the temperature of the fuel cell stack 23 is low, a process of supplying the fuel mixture to the activation burner by operating the mixture pump 41 in response to the activation request and heating the fuel cell stack 23 by the activation burner. I do.

[Overall Operation of Fuel Cell System 1]
As described above, in the first embodiment, as shown in FIG. 5, when it is determined that a serious abnormality has occurred at time t1, or the temperature of the fuel cell stack 23 is 400 ° C. due to a normal stop operation. When it falls below, the operation of the reforming water pump 7 is stopped (the instruction value to the reforming water pump 7 is lowered toward 0 so that the supply amount of the reforming water becomes 0), The supply valve 11 is switched from open to closed, and the discharge valve 29 is switched from closed to open.

As a result, the flow rate of the reforming water detected by the flow rate sensor 13 becomes zero.
After that, when restart is instructed at time t2, the operation of the reforming water pump 7 is resumed (the instruction value is quickly raised from 0), the supply valve 11 is switched from closed to open, and discharged. The valve 29 is switched from open to closed.

As a result, the flow rate of the reforming water detected by the flow rate sensor 13 quickly increases from 0 to a predetermined value.
c) Next, the effect of the present embodiment will be described.

  In this embodiment, since the supply valve 11 is provided between the filter 9 and the vaporizer 19 (and hence the reformer 21), when the operation of power generation in the fuel cell system 1 is stopped, the supply valve 11 modifies the supply valve 11. By closing the main flow path 3 of the quality water, it is possible to prevent the reformed water remaining between the filter 9 and the vaporizer 19 from flowing into the fuel cell stack 23 (specifically, the fuel cell).

  Further, when the fuel cell system 1 is stopped, the discharge valve 29 of the branch flow path 27 is opened to release the pressure of the reformed water (residual pressure) remaining between the filter 9 and the vaporizer 19. Therefore, at the time of restart (when operation is resumed), the supply valve 11 can be opened with the residual pressure lowered. Thereby, it is possible to prevent the reformed water from flowing into the fuel cell at the time of restart (due to excessive residual pressure).

In this way, in this embodiment, the reformed water can be prevented from flowing into the fuel cell, so that the fuel electrode can be prevented from being oxidized or damaged such as a cell crack of the fuel cell.
In particular, when the fuel cell is operated at a high temperature such as a solid oxide fuel cell, the fuel electrode is easily oxidized and the fuel cell is easily damaged. In this embodiment, the oxidation and damage are effectively prevented. Can be prevented.

Note that, as described above, by closing the reformed water main flow path 3 by the supply valve 11, damage to the catalyst filled in the reformer 21 can also be prevented.
Moreover, in this embodiment, the reforming water can be returned to the reforming water tank 5 from the main channel 3 between the filter 9 and the supply valve 11 by the branch channel 27, so that a reduction in the amount of reforming water is suppressed. can do.

  Further, in the present embodiment, the reformed water is discharged downstream from the filter 9, and therefore, after the restart, the purified reformed water that has passed through the filter 9 is supplied to the vaporizer 19 (and hence the reformer). 21 side).

  Moreover, in this embodiment, an ion exchange resin filter is used as the filter 9, and this ion exchange resin filter is always immersed in the reforming water, so that the inside of the filter 9 is always filled with the reforming water. However, the above-described control can prevent the performance of the filter 9 from deteriorating due to the backflow of the reformed water accumulated between the filter 9 and the supply valve 11 even when the operation is stopped.

  In this embodiment, the temperature of the side surface of the fuel cell stack 23 can be measured by the temperature sensor 25. Therefore, when the temperature of the fuel cell stack 23 is lowered to a sufficiently low temperature (for example, 400 ° C. or less) at which the fuel electrode is difficult to oxidize and the fuel cell is not easily damaged, the fuel cell system such as supply stop of the fuel gas. By stopping the operation of No. 1, it is possible to suppress oxidation of the fuel electrode and damage to the fuel cell.

Needless to say, the present invention is not limited to the above-described embodiments, and can be implemented in various modes without departing from the scope of the present invention.
(1) For example, the present invention is not limited to a solid oxide fuel cell (SOFC), but a solid polymer fuel cell (PEFC), a molten carbonate fuel cell (MCFC), a phosphoric acid fuel cell (PAFC) It can be applied to such fuel cells.

(2) Moreover, in the said Example, although a supply valve and a discharge valve are separate bodies, you may use the three-way valve provided with the function of the supply valve and the discharge valve.
Specifically, the three-way valve switches the flow path (main flow path) between the filter and the reformer and the branch flow path from the main flow path to the reforming water tank, that is, the main flow path. The flow path can be switched so that the branch flow path is closed when the channel is opened, and conversely, the branch flow path is opened when the main flow path is closed.

  Therefore, when the fuel cell system is in operation, the main channel is opened and the branch channel is closed, and when the operation is stopped, the main channel is closed and the branch channel is opened. This has the advantage that control of the opening and closing operation of the valve becomes easy.

DESCRIPTION OF SYMBOLS 1 ... Fuel cell system 3 ... Main flow path 5 ... Reformed water tank 7 ... Reformed water pump 9 ... Filter 11 ... Supply valve 13 ... Flow sensor 15 ... Power generation module 19 ... Vaporizer 21 ... Reformer 23 ... Fuel cell stack 25 ... Temperature sensor 27 ... Branch flow path 29 ... Discharge valve 31 ... Controller 33 ... Stop button 35 ... Start button

Claims (8)

Power generation having a vaporizer that vaporizes reformed water used to reform raw fuel into fuel gas, and a fuel cell stack in which fuel cells that generate power using the fuel gas and oxidant gas are stacked In a fuel cell system equipped with a module,
In the flow path for supplying the reformed water to the vaporizer,
From the upstream side,
A tank for storing the reformed water;
A pump for pumping the reformed water from the tank and supplying the reformed water to the vaporizer side downstream;
A filter that is retained in the reformed water and purifies the reformed water;
A supply valve disposed between the filter and the vaporizer for opening and closing the flow path;
A flow rate sensor disposed between the supply valve and the vaporizer to measure the flow rate of the reforming water in the flow path;
With
A branched flow path branched from the flow path between the filter and the supply valve and connected to the tank;
A discharge valve disposed in the branch flow path to open and close the branch flow path;
A fuel cell system comprising:   The fuel cell system according to claim 1, wherein the filter is an ion exchange resin filter.   The supply valve and the discharge valve are integrally configured as a three-way valve capable of switching the flow path of the reforming water between the flow path between the filter and the supply valve and the branch flow path. The fuel cell system according to claim 1, wherein the fuel cell system is a fuel cell system.   The fuel cell system according to claim 1, further comprising a temperature sensor that measures a temperature of the fuel cell stack.   The fuel cell system according to any one of claims 1 to 4, further comprising a reformer that reforms the raw fuel into the fuel gas on a downstream side of the vaporizer. In the control apparatus of the fuel cell system which controls the fuel cell system according to any one of claims 1 to 5,
When a condition for stopping the operation of the fuel cell system is satisfied,
Supply valve control means for controlling opening and closing of the supply valve;
A discharge valve control means for controlling opening and closing of the discharge valve;
Pump control means for controlling the operation of the pump;
A control apparatus for a fuel cell system, comprising: In the control method of the fuel cell system which controls the fuel cell system according to any one of claims 1 to 5,
When the condition for stopping the operation of the fuel cell system is satisfied, the supply valve controls to close the flow path between the filter and the supply valve, and the discharge valve opens the branch flow path. A control method for a fuel cell system, comprising performing control and control for stopping the pump.   The fuel cell system control method according to claim 7, wherein the condition for stopping the operation of the fuel cell system includes a condition in which a temperature of the fuel cell stack is equal to or lower than a predetermined temperature.

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